The present invention relates generally to control mechanisms and, more specifically, to a three-function control mechanism that employs a single control lever in order to actuate or move three separate actuators. The present invention further relates to a three-function control mechanism that is provided with a torque-amplifying device for assisting in the actuating of at least one of the actuators when the single control lever is operated. The present invention is particularly applicable for use on a work vehicle, such as a bulldozer or loader, in order to actuate hydraulic cylinders that control the positioning of a blade or shovel carried by the work vehicle.
Many bulldozers and loaders are provided with elaborate control systems that allow an operator to adjust or change the position of the blade or shovel. Without limiting the applicability of the present invention to the control of a bulldozer blade, the invention will be described hereinafter in connection with a bulldozer, it berg understood that the invention may be applicable to other work vehicles or other apparatus. Typically, the adjustments made by existing control systems to the bulldozer blade may include the following three movements: (1) raising and lowering of the blade; (2) the tilting of the blade about a first axis; or (3) angling of the blade about a second, mutually-perpendicular axis.
A typical bulldozer usually will have hydraulic cylinders that are coupled to the blade and that may be extended or retracted to change the position of the blade. The flow of hydraulic fluid to and from the hydraulic cylinders is typically controlled by corresponding valve systems that are actuated by movement of one or more control levers by the operator. Manipulation of more than one control lever in order to change the position of the blade can, however, be cumbersome to the operator. Furthermore, in one known control system where a single control lever is used, a significant number of parts are employed making the system relatively expensive to manufacture and assemble.
In many existing control systems, the operator may be required to twist the control handle in order to actuate one of the valve systems. The control handles usually must act against springs that are provided in the valve systems for holding the valve systems in a home or neutral position. Due to the limited available twisting motion of a human wrist, an operator may have difficulty overcoming the spring action and actuating one of the valve systems. When the operator twists the control handle, the handle can only move through a relatively short arc. This short arc produces a very limited lever advantage as compared to the lever advantage created when the control handle is moved either back and forth or side to side.
It is therefore desirable and an object of the present invention to provide a hydraulic control mechanism which features a single lever for actuating the valve systems. Another object is to provide a hydraulic control mechanism that has at least one torque-amplifying device for assisting in the actuating of the valve systems. It is a further object of the present invention to provide a hydraulic control mechanism that is relatively uncomplicated having relatively few main parts and which can carry out each of the three functions (lift, tilt, and angle) independently or in unison